HIV causes Acquired Immunodeficiency Syndrome (“AIDS”). The immune response to HIV infection in long-term non-progressors suggests that specific viral immunity may limit infection and the symptoms of disease. Some HIV infected individuals show broadly neutralizing IgG antibodies in their serum; little is known regarding the specificity and activity of these antibodies, despite their potential importance in designing effective vaccines, and no single characteristic has of yet been correlated with protective immunity. In animal models, passive transfer of neutralizing antibodies can contribute to protection against virus challenge. Neutralizing antibody responses also can be developed in HIV-infected individuals but the detailed composition of the serologic response is yet to be fully uncovered.
A number of immunologic abnormalities have been described in AIDS. These include, but are not limited to, abnormalities in B-cell function, abnormal antibody response, defective monocyte cell function, impaired cytokine production, depressed natural killer and cytotoxic cell function, defective ability of lymphocytes to recognize and respond to soluble antigens, and the depletion of the T4 helper/inducer lymphocyte population.
The amino acid and RNA sequences encoding HIV env from a number of HIV strains are known (Modrow, S. et al., J. Virology 61(2): 570 (1987)). The HIV virion is covered by a membrane or envelope derived from the outer membrane of host cells. This membrane contains a population of envelope glycoproteins (gp 160) anchored in the membrane bilayer at their carboxyl terminal region. Each glycoprotein contains two segments: the N-terminal segment, and the C-terminal segment. The N-terminal segment, called gp120 by virtue of its relative molecular weight of about 120 kD, protrudes into the aqueous environment surrounding the virion. The C-terminal segment, called gp41, spans the membrane. The N-terminal gp120 and the C-terminal gp41 are covalently linked by a peptide bond that is particularly susceptible to proteolytic cleavage. See European Patent Application Publication No. 0 335 635 to McCune et al and the references cited therein, each incorporated herein by reference in its entirety.
Several approaches to an AIDS vaccine have been proposed, including, but not limited to, inactivated and attenuated virus vaccines, subunit vaccines from virus-infected cells, recombinantly produced viral antigens, vaccines based on synthetic peptides, anti-idiotypic vaccines, and viral carrier-based vaccines. An additional approach to HIV therapeutic and prophylactic treatment includes making highly potent, broadly neutralizing monoclonal antibodies. Multiple studies have reported cloning and making monoclonal antibodies by various techniques for targeting the CD4 binding site as well as other parts of the virion spike and for neutralizing HIV. Generally, these techniques involve self-fusion or phage display techniques. Typically, in making HIV neutralizing antibodies using phage display techniques, random combinations of heavy and light chains are combined and a random pair is selected. Studies have reported a limited number of monoclonal antibodies, such as, for example, the phage display antibody b12, that are broadly highly potent, and broadly neutralizing (meaning antibodies that can neutralize multiple strains of HIV in sera) against HIV. The monoclonal antibody b12 is a broadly neutralizing antibody which has been reported to prevent HIV infection in macaques. Another broadly neutralizing antibody includes 2G12, which, atypically, has a structure which has yet to be seen in any other antibody with three combining sites. VRC01 is recently discovered broadly neutralizing antibody that targets the CD4 binding site (CD4bs) on the HIV spike. VRC01 was isolated by purifying single B cells that bind to a soluble, biotin labeled, stabilized, and re-surfaced core fragment of HIV gp120 (X. Wu et al., Science 329, 856 (Aug. 13, 2010)). Although successful, the isolation was inefficient, producing only 3 closely related HIV-binding antibodies from 25 million peripheral blood mononuclear cells from one individual. Like other anti-HIV antibodies obtained by the single cell antigen capture method, VRC01-3 showed very high levels of somatic mutations that were essential for potency and breadth. This high frequency of mutation is a potential impediment to antibody cloning because the mutated sequences may no longer be complementary to the primers used for cloning.
Some studies have reported that certain patients develop antibodies to HIV that are broadly neutralizing. Studies have reported that antibodies can be protective against initial HIV infection in passive transfer experiments in non-human primates and can modulate viral load during infection. See, for example, Mascola, 2000; Shibata, 1999; Veazey, 2003; Parren, 2001; Mascola, 1999; Trkola, 2005; Wei, 2003; Frost, 2005; Burton, 2004; Mascola, 2007; Karlsson Hedestam, 2008; McMichael, 2006; Zolla-Pazner, 2004.